Preparation of Si-SiOx nanoparticles from volatile residue produced by refining of silicon

Abstract

Residual Si was produced on a furnace wall when upgraded metallurgical grade Si was refined by electron beam melting. It was then recycled to prepare Si-SiO_x nanoparticles with an average size of 100 nm by planetary ball milling. The obtained Si-SiO_x nanoparticles mainly consist of amorphous Si, crystalline Si and amorphous SiO_x, which was confirmed by XRD, FTIR, XPS and TEM. SiO_x is mainly composed of SiO₂ and SiO_1.35. Distilled water used as a grinding aid not only enhances milling efficiency, but also plays a key role in obtaining SiO_x. During refining of upgraded metallurgical grade Si, the deposition pattern of residual Si on furnace wall agrees with model of three-dimension growth. Growth of Si-SiO_x nanoparticles is the mutual effect of distilled water and ball milling. Si-SiO_x nanoparticles were doped into phenolic resin pyrolysis carbon as anode materials for lithium ion batteries, and 10% doping was observed to improve the specific capacity. After 500 cycles, specific capacity of delithiation remained around 550 mA h/g. It suggests the residual Si is a value-added by-product, and it can be recycled as anode materials for lithium ion batteries.

Keywords: Electron beam melting; Planetary ball milling; Residual Si; Si-SiO(x) nanoparticles; Si-carbon anode.